The present invention relates to a sound reproduction apparatus; and more specifically, to a sound reproduction apparatus having a superior capability of positioning the acoustical image in a certain specific place. The capability provides a significant advantage when it is installed in the room of an automobile body. The invention also relates to a speaker unit used in the sound reproduction apparatus.
Car-borne loud speakers are mounted, in most cases, in front doors, or the like places in the room of an automobile body. Under such a speaker layout, it is not easy to place the acoustical image at a location in the central front area. In order to have the acoustical image placed at the central front area, it has been a normal practice to install a center speaker apparatus dedicated to reproduction of middle-range frequency sound at the center of a dashboard, or other place in the central front space in the room of an automobile body, the place being located in the middle between a left channel speaker apparatus and a right channel speaker apparatus.
A conventional center speaker apparatus is described in the following. FIG. 17 is an exploded perspective view of a conventional center speaker apparatus. Referring to FIG. 17, a front baffle 1702 is for holding a speaker unit 1701 thereon. A cabinet 1703 and the front baffle 1702 enclose the rear sound output of the speaker unit 1701. A voltage amplifier 1704 mixes the left channel sound input signals and the right channel sound input signals together, and delivers only the middle range frequency sound signals of the mixed signals through a band pass filter. A power amplifier 1705 amplifies the sound signals from voltage amplifier 1704, and delivers them to the speaker unit 1701. A power supply 1706 supplies power to the voltage amplifier 1704 and the power amplifier 1705. A radiator 1707 dissipates heat generated at the power amplifier 1705.
FIG. 18 is a block diagram, which describes a setup with the conventional center speaker apparatus used in a car-borne application. In FIG. 18, a left channel speaker apparatus 1801 is mounted in a front door at a passenger seat, while a right channel speaker apparatus 1802 is mounted in a front door at a driver seat. A center speaker apparatus 1803 is provided at the center, or in the central front space of an automobile body, and reproduces only the middle range frequency sounds. A sound source 1804 comprises a program source, such as a CD player, an FM/AM tuner, and a power amplifier which drives the left and the right speaker apparatuses 1801, 1802.
FIG. 19 illustrates a layout of speakers in an automobile room, using the conventional center speaker apparatus.
Now in the following, operation of the above-described conventional center speaker apparatus is described.
Referring to FIG. 18, sounds are reproduced by the left channel speaker apparatus 1801 and the right channel speaker apparatus 1802, both connected to the sound source 1804. Sound output signals from the program source of the sound source 1804 are also sent to the conventional center speaker apparatus 1803. The sound signals sent from the program source of the sound source 1804 are led to the voltage amplifier 1704, shown in FIG. 17; where, the left channel sound signal and the right channel sound signal are mixed and converted into monaural signals. The mixed sound signals are sent through a band pass filter, so that only the middle range frequency sound signal components responsible to the vocal region are supplied. The sound signals sent from the voltage amplifier 1704 are amplified at the power amplifier 1705 and drive the speaker unit 1701. Then, a sound is reproduced from the speaker unit 1701.
FIG. 19 shows a location of the conventional center speaker apparatus 1803 installed in the room of an automobile body. The speaker apparatus 1803 is placed in the central part of the dashboard, and the speaker apparatus 1803 generates the middle range sound centered in vocal region. By so doing, the acoustical image can be positioned naturally in the central front area without ill-affecting the stereophonic sound feeling.
In this way; namely, by providing a middle-range-dedicated center speaker apparatus at the center, or in the central front area between the left channel speaker apparatus and the right channel speaker apparatus; the natural sound environments having the acoustical image positioned at the central front space may be implemented without sacrificing the stereophonic sound feeling, even in such car-borne cases where the locations for installing speakers are limited, for example, to front doors, hence, positioning the acoustical image in the central front space is difficult.
Thus, the conventional center speaker apparatus can provide natural sound environments with the acoustical image positioned at the central front space. However, the conventional center speaker apparatus requires extra items such as a voltage amplifier 1704, a power amplifier 1705, a power supply 1706, a radiator 1707 or the like, in addition to the basic constituent members, such as the speaker unit, the front baffle and the cabinet. These extra items have been a blocking factor against the efforts to reduce the size and weight of such a speaker apparatus.
The present invention addresses the above problems and aims to offer a compact, light-weight, simple-structured center speaker apparatus, where the voltage amplifier, the power amplifier, the power supply and the heat radiator are eliminated.
A sound reproduction apparatus of the present invention comprises:
a left channel speaker apparatus for receiving a sound output signal delivered from the left channel of a sound source,
a right channel speaker apparatus for receiving a sound output signal delivered from the right channel of the sound source, and
a center speaker apparatus disposed at the center, or in the central front space between the speaker apparatuses for the left and the right channels.
A speaker unit of the center speaker apparatus is provided with a left-channel voice coil for receiving the left channel sound output signal and a right-channel voice coil for receiving the right channel sound output signal. These voice coils are disposed in a co-axial arrangement.
The speaker unit of the present invention comprises, like conventional speaker units, a diaphragm coupled with a voice coil bobbin, a suspending means to mechanically suspend the diaphragm and the voice coil bobbin, and a magnetic circuit for providing magnetic flux for the two voice coils. A frame for mounting the suspending means and the magnetic circuit thereon is of course included. The center speaker apparatus of the present invention is formed only of the above-described speaker unit, a front baffle and a cabinet; amplifying items indispensable to the conventional center speaker apparatus have been eliminated.
The center speaker apparatus of the present invention eliminates the voltage amplifier, the power amplifier, the power supply and the heat radiator, and has a simplified structure. Thus, the center speaker apparatus can be made compact and light in weight.